1. Field of the Invention
The present invention relates to a polishing method and an apparatus for removing corner material penetrated into a corner formed by a side wall of an insulation film on a semi-conductor wafer and a front surface of the wafer.
2. Background of the Invention
FIGS. 1A to E are illustrative drawings for illustrating a part of processing of semi-conductor wafer surface. A semi-conductor wafer W is a circular plate having a front plane surface 2p, a back plane surface 2q, a front beveled surface 2a, a back beveled surface 2b, and a side surface 3. An insulation film I made of silicone oxide film is formed on the front plane surface 2p of the semi-conductor wafer W (FIG. 1A). Next, trenches or grooves T for forming a wiring are formed on the insulation film I (FIG. 1B), and further, a metal film M is formed on an oxide film I (FIG. 1C). At this time, the metal is penetrated into the trenches. The film M is removed so as to leave the metal in the trenches T (FIG. 1E). The metal remaining in the trenches T become the wirings of a semi-conductor device.
From the nature of the metal film forming method, unnecessary metal film portions M1, M2, M3 are formed on the external area of the insulation film area, namely on a part of the front plane surface 2p and on the surfaces 2a, 3 and 2b. 
In order to remove the metal film M on the oxide film I to form the wirings, a chemical mechanical polishing (CMP) process is performed. In the CMP process, if a part of the metal film M peels off and the peel fragment is engaged between the oxide film and a polishing tool, the oxide film surface is scratched. The scratches decrease the yield of the semi-conductor device manufacturing and moreover metal film portions M1, M2, M3 are easy to peel off. Therefore, these metal film portions M1, M2, M3 are removed before the CMP process (FIG. 1D).
It should be appreciated that a swell called xe2x80x9creboundxe2x80x9d is sometimes left on the oxide film when the CMP process is performed without removing the metal film portions M1, M2, M3. When the xe2x80x9creboundxe2x80x9d is removed in a separate process, the necessary portion tends to be removed and therefore the uniformity of the film thickness is deteriorated. From the respect also, it is extremely difficult to perform the CMP process with the metal films M1, M2, M3 attached.
Japanese Laid-Open Patent Application No. 2000-068273 discloses a technology for removing the metal film of the periphery of the insulation film I after removing the metal film on the surface of the insulation film I by the CMP method. The technology takes into consideration a fact that the metal film of the periphery thereof is easily contaminated in the following process and the contaminated film tends to peel off, and is characterized by that it is performed after the CMP process. Therefore, this does not solve the problem that the metal film of the periphery peels off during the CMP process as in the present invention.
Japanese Patent Application Laid-Open No. Hei No. 10-312981 (Patent No. 3111928) discloses the removal of metal film of the periphery thereof, before removing the metal film M on the insulation film I by the CMP method. The removing of metal film of the periphery is performed by submerging the entire wafer into an oxidant solution in an etching vessel, or by pressing the wafer to a polishing pad so that the wafer periphery penetrates into the pad under the pressure.
In the former case, it is supposed that a metal film of an appropriate thickness of such a order allowing to perform the CMP can be left on the insulation film, when the peripheral metal film is removed. However, as the method depends on an etching speed, it is not reliable, and moreover it causes a problem that an optimal kind of etching solution must be selected.
The problem of the dependency on the etching speed can be solved by protecting the metal film on the insulation film from etching with a masking, there is caused, however, another problem of implementation of masking process or a process for removing the same. In either case, as it is impossible to remove the peripheral metal film perpendicularly to the semi-conductor wafer base member from the insulation film, a part of a metal film Mxe2x80x2 (FIG. 1D) remains at the corner portion of the insulation film and the semi-conductor wafer base member. This will peel off in the following CPM process, causing scratch.
On the other hand, in the latter case (removing method for pressing the wafer periphery to the polishing pad so that it penetrates into the pad under the pressure), the point that can be polished depends on the deformation of the polishing pad, and the polishing effect is not exerted sufficiently up to the corner portion, leaving a part of the metal film Mxe2x80x2 (FIG. 1D) easily. As in the former case, this will peel off in the following CPM process, causing scratch.
It is an object of the present invention to provide a method and an apparatus for removing substantially completely the metal film portions M1, M2 and M3 of the metal film M of the semi-conductor wafer periphery, before a chemical mechanical polishing of the metal film on the insulation film surface. Moreover, it is another object of the present invention to prevent peel fragments from being engaged between the oxide film and a polishing tool during the CMP process, and thereby to improve the yield of the semi-conductor device manufacturing.
According to the present invention, in a semi-conductor wafer where a metal film is formed on the surface of the insulation film and the surface of a periphery thereof where the insulation film is not formed, the metal film of the periphery thereof is removed before chemical mechanical polishing of the metal film on the insulation film surface. The metal portion penetrated in the corner portion formed by the side wall of the insulation film and the surface of the semi-conductor base member that it is extremely difficult to be removed by the conventional removal method, can be removed substantially completely by the effect of a rotary driven polishing member, and a slurry supplied to a polished portion. The semi-conductor wafer from which the peripheral film including the metal portion of the corner portion is removed is rinsed with pure water, and transferred to the CMP process for removing the metal film on the insulation film surface. As there is no metal portion in the corner portion, the metal portion will never peel off during the CMP process. Therefore, peel fragments engaged between the polishing member and the insulation film will not cause a scratch on the insulation film surface.
In the polishing apparatus of the present invention, a rotary corner polishing member is positioned to align its edge with the edge of the insulation film and a pressing means apply the corner polishing member to the metal film of the periphery thereof. The metal film of the periphery thereof including metal portions of corner portions is removed substantially completely by the rotary driven polishing member and slurry supplied to the polished portion.
Other objects and advantages besides those discussed above shall be apparent to those skilled in the art from the description of a preferred embodiment of the invention which follows. In the description, reference is made to accompanying drawings, which form a part thereof, and which illustrate an example of the invention. Such example, however, is not exhaustive of various embodiments of the invention, and therefore reference is made to the claims which follow the description for determining the scope of the invention.